Engine systems may utilize recirculation of exhaust gas from an engine exhaust system to an engine intake system (intake passage), a process referred to as exhaust gas recirculation (EGR), to reduce regulated emissions. An EGR system may include various sensors to measure and/or control the EGR. As one example, the EGR system may include an intake gas constituent sensor, such as an oxygen sensor, which may be employed to measure oxygen to determine the proportion of combusted gases in an intake passage of the engine. Further, the sensor is sensitive to total pressure. As such, the sensor may be sensitive to diluents such as ambient humidity, exhaust humidity, and carbon dioxide. Due to equilibration of the sensed gas by a catalyzing sensing element of the sensor, the oxygen sensor is sensitive to both the partial pressure of oxygen and the presence of fuel (or other reductants and oxidants). As such, the sensor may be sensitive to oxidants and reductants such as oil mist and fuel vapor. Thus, the sensor measurements may be confounded by the various sensitivities, and the accuracy of the sensor, and thus, measurement and/or control of EGR, may be reduced.
The inventor herein has recognized the above issue and have devised an approach to at least partially address it. Thus, a method for an engine system is disclosed. The method includes, based on outputs from a catalyzing sensor and a non-catalyzing sensor, indicating an intake oxygen concentration and a fuel vapor concentration. The method further includes adjusting EGR responsive to the oxygen concentration, and adjusting fuel injection responsive to the fuel vapor concentration.
In such an example, the non-catalyzing sensor is used to determine an amount of EGR and the difference between the catalyzing sensor output and the non-catalyzing sensor output is used to determine an amount of fuel vapor. By using a non-catalyzing sensor, equilibration at a sensing surface of the sensor is reduced such that fuel vapor acts as a diluent instead of directly reducing the measured oxidant level. As such, EGR may be measured and controlled with increased accuracy. Further, a difference in output between the catalyzing sensor and the non-catalyzing sensor may be indicative of the fuel vapor concentration. In this way, an operating parameter such as fuel injection may be adjusted responsive to the fuel vapor concentration in the intake passage.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.